The spine is a flexible column formed of a plurality of bones called vertebrae. The vertebrae are hollow and piled one upon the other, forming a strong hollow column for support of the cranium and trunk. The hollow core of the spine houses and protects the nerves of the spinal cord. The different vertebrae are connected to one another by means of articular processes and intervertebral, fibrocartilaginous bodies. Various spinal disorders may cause the spine to become misaligned, curved, and/or twisted or result in fractured and/or compressed vertebrae. It is often necessary to surgically correct these spinal disorders.
The spine includes seven cervical (neck) vertebrae, twelve thoracic (chest) vertebrae, five lumbar (lower back) vertebrae, and the fused vertebrae in the sacrum and coccyx that help to form the hip region. While the shapes of individual vertebrae differ among these regions, each is essentially a short hollow shaft containing the bundle of nerves known as the spinal cord. Individual nerves, such as those carrying messages to the arms or legs, enter and exit the spinal cord through gaps between vertebrae.
The spinal disks act as shock absorbers, cushioning the spine, and preventing individual bones from contacting each other. Disks also help to hold the vertebrae together. The weight of the upper body is transferred through the spine to the hips and the legs. The spine is held upright through the work of the back muscles, which are attached to the vertebrae. While the normal spine has no side-to-side curve, it does have a series of front-to-back curves, giving it a gentle “S” shape. If the proper shaping and/or curvature are not present due to scoliosis, neuromuscular disease, cerebral palsy, or other disorder, it may be necessary to straighten or adjust the spine into a proper curvature.
When one or more disks degenerate through accident or disease, nerves passing near the affected area may be compressed and are consequently irritated. The result may be chronic and/or debilitating back pain. Various methods and apparatus have been designed to relieve such back pain, including spinal fusion using an interbody spacer or suitable graft using techniques such as Anterior Lumbar Interbody Fusion (ALIF), Posterior Lumbar Interbody Fusion (PLIF), or Transforaminal Lumbar Interbody Fusion (TLIF) surgical techniques. The implants used in-these techniques, also commonly referred to as vertebral body replacements (VBR) devices, are placed in the interdiscal space between adjacent vertebrae of the spine. Many times an exterior plate is used in conjunction with the VBR to hold the adjacent vertebrae while the fusion occurs.
Ideally, the interbody spacer should stabilize the intervertebral space and allow fusion of the adjacent vertebrae. Moreover, during the time it takes for fusion to occur, the interbody spacer should have sufficient structural integrity to withstand the stress of maintaining the space without substantially degrading or deforming and have sufficient stability to remain securely in place prior to actual bone ingrowth fusion.
One significant challenge to providing fusion stability (prior to actual bone ingrowth fusion) is preventing spinal extension during patient movement. Distraction of the vertebral space containing the fusion graft may cause the interbody spacer to shift or move disrupting bone ingrowth fusion and causing pain. An exterior plate is often used with the interbody spacer to hold the adjacent vertebrae while the fusion occurs.
Currently, a surgeon is limited to using his or her line of sight to align the interbody cage and plate. There remains a need for an attachment guide for aligning an interbody spacer and an anterior cervical plate during insertion and implanting in a patient.